1. U.S. Government Accountability Office. (2012, July). STRATEGIC SOURCING: Leading Commercial Practices Can Help Federal Agencies Increase Savings (GAO-12-677). In Figure 1, "A Seven-Step Strategic Sourcing Process," the first step is explicitly defined as "Analyze agency-wide spending" (p. 8).
2. Monczka, R. M., Handfield, R. B., Giunipero, L. C., & Patterson, J. L. (2016). Purchasing and Supply Chain Management (6th ed.). Cengage Learning. Chapter 7, "The Strategic Sourcing Process," outlines the initial steps as building a team and conducting market intelligence research, which is fundamentally driven by a detailed spend analysis to understand the current purchasing profile before engaging the market.
3. Smeltzer, L. R., & Siferd, S. P. (1998). Proactive supply management: The management of risk. International Journal of Purchasing and Materials Management, 34(1), 38-45. The article emphasizes that strategic supply management begins with a thorough analysis of the firm's expenditures (spend analysis) to identify critical categories and formulate appropriate strategies.